The present invention relates to a gun tube having a spin curve with a variable spin angle and a rifling force R(x) over the path of the projectile that becomes effective when a projectile is fired. The gun tube further has a given caliber d, projectile mass m.sub.G, a moment of mass inertia J about the longitudinal axis of the projectile, a gas pressure force P(x) on the projectile bottom, and a projectile velocity v(x).
According to the book entitled "Waffentechnisches Taschenbuch" [Handbook on Weaponry], published by Rheinmetall GmbH, Dusseldorf, 1980, gun tubes of this type are known in which various types of spin may be provided which cause different rifling force curves over the movement of spin stabilized projectiles. Constant and parabolic spin curves are employed most frequently. However, in these cases, the ideal rifling force curve is realized at most in an approximation, although the equation for the rifling force over the projectile path in the gun tube is known from this publication in a good approximation as ##EQU2## where d is the caliber of the gun tube, m.sub.G is the weight of the projectile, J is the moment of inertia of the masses about the longitudinal axis of the projectile, P(x) is the force of the gas against the projectile bottom and v(x) is the velocity of the projectile.
German Patent No. 3,409,073 discloses the optimization of spin in the gun tube relative to certain characteristics by means of a polynomial, while DE-OS [Unexamined Published German Patent Application] 4,001,130 discloses the realization of the same with the aid of breaking up the spin angle into a Fourier series. Here again, no ideal rifling force curve results and correspondingly these solutions have advantages and disadvantages.